Dehairing of hides



Sept. 26, 1950 R. A. WHITMORE DEHAIRING OF HIDES Filed April 5, 1946Inventor Faber? A. W/z/fmore By his Attorney Patented Sept. 26, 1950DEHAIRING or HIDES Robert A. Whitmore, Beverly, Mass, assignor to UnitedShoe Machinery Corporation, Flemington, N.;J., a corporation of NewJersey Application April 5, 1946, Serial N0. 659,699

5 Claims.

This invention pertains to improvements in methods for dehairing hidesand skins by the use of liquid chemical agents.

For the purpose of eliminating verbiage in the present application, theterm wet untanned hides" is used and is intended to refer to both hidesand skins secured from the fiaying operation without any substantialalteration and also to salted untanned hides or skins which have beenwet back to such an extent that the electrolytic content has beenreduced and approximates that of fresh hides or skins.

It is one of the objects of the present invention to increase the speedwith which the dehairing operation may be carried out. Another object isto provide a method which is not only rapid but which leaves noappreciable harmful efiects as to the quality of the hide and theremoved hair.

With these ends in view, the invention contemplates the limited use of adehairing solution of an electrolytic nature, not as a bath forsubmerging the hide but merely as an agent for wetting the hair to beremoved. An electric current is then passed through the hide, the hairof which is thus treated, and this passage is preferably from the fleshside to the hair side, i. e., the cathode is preferably on the hair sideand the anode on the flesh side. As a consequence, the hair is loosenedand may be easily scraped or slipped from the hide without appreciableinjury to either the hide or the hair.

These and other important features of the invention will be described indetail in the specification and pointed out in the appended claims.

In the drawing, the figure is a diagrammatic and perspective iew of oneform of the apparatus suitable for carrying out the method, part of theapparatus being broken away to show the hide being treated.

The apparatus for carrying out the method may be simple in nature and asdisclosed includes a plate In of such size as to exceed the size of anywork piece to be treated. As shown, a hide l2 to be dehaired issupported for treatment with its flesh-side against the plate 50. Thehair I4 of the hide I2 is moistened with an electrolytic solution and ascreen [6 is placed thereupon. Two cross-bars l8 and 20 are preferablysoldered to the screen [6 and the bar I8 at a medial point is providedwith an electrical connection 22 to the line 24 leading to the negativeside of a battery or source of current 26. The positive side ofthesource of current is provided with a line 28 connected to the plate illat plate in pl e of plat It. It is to be understood that the plate In isfree of the electrolytic solution as applied to the hair l4. Under suchconditions it is clear that the flesh side of the work piece will befree of the applied electrolyte dur-- ing the treatment. In place of thescreen IS, a. perforated plate, spaced bars or some other form. ofcontact means may be utilized although it is; essential that whateverform electrode is used upon the hair side of the work piece, suchelectrode should be vented to permit gases to emanate.

The preferred material for the electrodes is aluminum as no stains areproduced upon the hides when it is used. It should be understood,

3 however, that other materials may be used for the electrodes. This isseen to be so, particularly when it is understood that stains are oftenunobjectionable for certain uses of the leather ultimately produced fromthe dehaired hide.

It has been determined that either direct or alternating current may beused although direct current is preferable and has less tendency to heatthe hide unduly. Direct current in reverse (using the plate [0 as thecathode instead of as the anode) will serve to unhair hides but not asrapidly as occurs when the hair side is against the negative electrode.The voltage should not be higher than 24 volts if shrinkage of the hidesis to be avoided. Amperage will, of course, vary with the size of thework piece and depending uponthe concentration of the electrolyte. It ispreferable, however, to use suflicient amperage to avoid prolongedcontact of the hair with the electrolytic solution as such contact maysoften the hair excessively. j

A number of electrolytic solutions have been used with varying degreesof success and such solutions have varied in concentration from veryWeak solutions up to 50% and have been alkaline or approximatelyneutral, i. e., their pH value has been above approximately 7. Simpleexperimentation with various solutions and difierent types of skinsquickly determines the proper concentration to use. Sodium hydroxide,for example, has been used up to a concentration of 20% at whichconcentration dehairing has satisfactorily taken place but the hairsufiered damage. The quality of both hair and hide was retained when theconcentration of sodium hydroxide was reduced to .5 or 1%. I

' Excessive care need not be used in applying the solution selected tothe hair as the hair appears to absorb it by capillary attraction andthe hide is quite resistant against penetration by the solution.

The tests have been carried on successfully at difierent temperaturesvarying from approximately room temperature up to approximately bodytemperature,

It is preferable to wash the products immediately subsequent to theunhairing step in order that any deleterious action by the unhairingsolution be prevented.

It has also been found preferable although not essential to add adiluting agent such as methanol or phenol to the solution. Such additionmakes possible a more uniform and satisfactory dehairing operationprobably because any tendency for short-circuiting is appreciablyovercome.

The following specific examples are merely illustrative of the methodswhich may be used in carrying out the principles of this invention, thework piece in each instance being a fresh piece of calfskin:

Example 1 Example 2 Dehairing solution: 1% KOH, no alcohol.

Current: Direct, 6 volts, 3 amperes at first for each 3" x unit of skinarea reduced to .8 ampere in 3 minutes.

Time of treatment: 7 minutes.

Results: Both hair and skin of satisfactory quality. Hair easilyremoved.

Example 3 Dehairing solution: 3% LiOl-I, no alcohol.

Current: Direct, 6 volts, 3 amperes reducing to about .8 ampere (foreach 3" x 5" unit of skin area).

Time of treatment: 5 minutes.

Results: Both hair and skin of good quality.

Hair easily removed.

Example 4 Dehairing solution: 3% NaCl, no alcohol. Current: Direct, 6volts, 3 amperes reducing to .5 ampere (for each 3 x 5" unit of skinarea).

Time of treatment: 5 minutes.

Results: Products good but hair slightly overheated. Hair did not slipas well as with the use of alkaline substances.

Example 5 Dehairing solution: 5% NaCeI-IaO (sodium phenolate) noalcohol.

Current: Direct, 6 volts, 1.5 amperes down to .5 ampere (for each 3 x 5"unit of skin area).

Time of treatment: minutes.

Results: Products good and hair was removed easily although not soeasily as in Examples 1, 2 and 3.

Example 6 Dehairing solution: 5% Na2SzO3.5HzO (sodium thiosulfate)Current: Direct, 24 volts, 3 amperes (for each 3 x 5" unit of skinarea).

Time of treatment: About 3 minutes.

Results: Ease of unhairing and quality of products both satisfactory.

Example 7 V I .Dehairing solution: 2.4% NaOH and 2% C'sHsO (phenol).

Current: Direct, 6 volts, 1.5 amperes at first reducing to 1 ampere (3"x 5").

Results: Unhairing easily done and products of good quality althoughskins were horsed up for 30 minutes without Washing.

Having described my invention, what I claim as new and desire to secureby Letters Patent of the United States is:

1. The method of dehairing a wet untanned hide having an electrolyticcontent approximately that of a fresh hide which comprises theapplication of an electrolytic solution having a pH value aboveapproximately seven to the hair side only of such a hide, spreading outand pressing the hide between two electrodes, and passing an electriccurrent through the thickness dimension of the hide while one of saidelectrodes is free of said electrolytic solution.

2. The method of dehairing a wet untanned hide having an electrolyticcontent approximately that of a fresh hide which comprises applicationof a dilute electrolytic alkaline solution to the hair side only of sucha hide, spreading out and pressing the hide between two aluminumelectrodes, and passing a direct current through the thickness dimensionof the hide from one aluminum electrode to the other while said otherelectrode is free of said applied solution.

3. The method of dehairing untanned wet hides each having anelectrolytic content not in excess of that in a fresh hide whichcomprises the application of an alkaline electrolytic solution to thehair side only of such a hide, spreading out and pressing the hidebetween two electrodes, passing an electric current through the hide forsufficient time to loosen the hair while one of said electrodes is freeof said solution, and subsequently removing the loosened hair from thehide.

4. The method of dehairing \vet untanned hides each having anelectrolytic content approximately that of a fresh hide which comprisesthe application of an electrolytic solution having a pH value aboveapproximately seven to the hair side only of such a hide, and passing adirect current through the hide from the flesh side to loosen the hairwhile the flesh side is free of the applied solution.

5. The method of dehairing wet untanned hides each having anelectrolytic content approximately that of a fresh hide which comprisesthe spreading out of such a hide, aplying an electrolytic solutionhaving a pH value above approximately seven to the hair side only,passing an electric current through the hide from the flesh side tothe-hair side while the fiesh'side is free of said applied solution, thesaid current being of suflicient intensity to loosen the hair, andsubsequently removing the loosened hair from the hide.

ROBERT A. 'WHITMORE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 653,716 Van Gestel July 1'7, 1900683,836 Berget Oct. 1, 1901 737,882 Strecker Sept. 1, '1903 976,036Burton Nov. 15, 1910 FOREIGN PATENTS Number Country Date 4,488 GreatBritain 1- Sept. 16, 1909 Certificate of Correction Patent No. 2,523,486September 26, 1950 ROBERT A. WHITMORE It is hereby certified that errorappears in the printed specification of the above numbered patentrequiring correction as follows:

Column 4, between lines 2 and 3, insert Time of treatment: 10 minutes;

and that the said LettersPatent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 3rd day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

1. THE METHOD OF DEHAIRING A WET UNTANNED HIDE HAVING AN ELECTROLYTICCONTENT APPROXIMATELY THAT OF A FRESH HIDE WHICH COMPRISES THEAPPLICATION OF AN ELECTROLYTIC SOLUTION HAVING A PH VALUE ABOVEAPPROXIMATELY SEVEN TO THE HAIR SIDE ONLY OF SUCH A HIDE, SPREADING OUTAND PRESSING THE HIDE BETWEEN TWO ELECTRODES, AND PASSING AN ELEC-